This invention relates to compositions for paint and coating removal. More particularly, this invention relates to compositions containing alkylene carbonate or dialkyl carbonate or both, hydrogen peroxide, and water.
Paint removing compositions are commonly used in industry, such as for stripping paint from airplane fuselages. Conventional paint remover compositions include methylene chloride, phenol, or caustic. Each of these materials, however, has inherent problems during use. While methylene chloride based compositions are very effective as paint removers, methylene chloride is a highly volatile material which is considered toxic. Similarly, phenol is highly toxic. Furthermore, caustic causes burns and attacks aluminum. Due to the deficiencies and disadvantages of conventional paint removing compositions, new paint removing compositions are highly desirable.
In one broad respect, this invention is a composition useful as a paint remover, comprising: alkylene carbonate, hydrogen peroxide, and water. This composition may also contain dibasic ester.
In another broad respect, this invention is a process for removing paint, comprising: applying a composition containing alkylene carbonate, hydrogen peroxide, and water to a painted surface for a time and under conditions effective to cause blistering or bubbling of the paint. The composition used therein may also contain dibasic ester.
In another broad respect, this invention is a process for removing paint, comprising: applying a composition containing (a) alkylene carbonate, dialkyl carbonate, or both, (b) hydrogen peroxide, and (c) water to a painted surface for a time and under conditions effective to cause blistering or bubbling of the paint. The composition used therein may also contain dibasic ester.
In another broad respect, this invention is a composition useful as a paint remover, comprising: dialkyl carbonate, hydrogen peroxide, and water. This composition may optionally contain an alcohol, a glycol ether, an alkylene carbonate, or a combination thereof This composition may instead include dibasic ester.
In another broad respect, this invention is a process for removing paint, comprising: applying a composition containing dialkyl carbonate, hydrogen peroxide, and water to a painted surface for a time and under conditions effective to cause blistering or bubbling of the paint. The composition used therein may also contain dibasic ester.
The surfaces to be treated may be sealed with a variety of sealants, such as polysulfide, polyurethane, lacquer, epoxy, and the like. The compositions can be used to remove paints and coatings from furniture, automobiles, boats, trains, airplanes, military vehicles, and so forth.
This invention has a number of advantages. For example, the compositions have several important attributes, including low toxicity, high efficacy in removing paint and coatings, and neutral pH (or slightly acidic or slightly basic pH). Furthermore, in the case of propylene carbonate, the propylene carbonate breaks down into propylene glycol, which is non-toxic. Likewise, hydrogen peroxide decomposes over time to water. Hence, the propylene carbonate compositions of this invention are environmentally friendly, particularly as compared to chlorinated hydrocarbons and the like which are commonly used for paint and coating removing. In addition, the compositions of this invention cause blistering and bubbling in such a short period of time that it is envisioned that the compositions of this invention might be applied in liquid form, as opposed to the gels which are commonly applied which lesson evaporation of the chlorinated hydrocarbons, for example.
It has further been advantageously found that by employing hydrogen peroxide in the form of an at least 50% aqueous solution, a miscible solution forms with alkylene carbonate. In the context of this invention, by miscible solution it is meant a single phase solution. The resulting composition has surprisingly superior paint removing properties, which is believed to be due to the limited amount of water present. The compositions may be blended with additional cosolvents, activators, corrosion inhibitors, and the like, or may be used directly to effect paint removal. The compositions of this invention may advantageously be non-flammable, of low volatility and free of carcinogenic chemicals.
The compositions of this invention contain alkylene carbonate or dialkyl carbonate or both, hydrogen peroxide, and water.
The hydrogen peroxide and water can be conveniently obtained from commercial sources as aqueous hydrogen peroxide solutions of varying percentages. Hydrogen peroxide is commonly available in aqueous solutions at a concentration of from about 1 to about 80 percent. For example, industrial solutions are often 30 percent or more by weight hydrogen peroxide solutions. It has been found that in the practice of this invention, the use of a 50% aqueous hydrogen peroxide solution is particularly effective. It may be appreciated that highly concentrated hydrogen peroxide should be handled carefully and appropriately since such materials are considered strong oxidizers. It may also be noted that once the concentrated hydrogen peroxide solution is admixed with carbonate, the concentration of hydrogen peroxide decreases which thus reduces the hazardous nature of the final composition. For example, when the overall concentration of hydrogen peroxide in the admixed composition is less than about 30%, special precautions need not be taken to handle the composition. Use of an aqueous hydrogen peroxide solution having a concentration of from about 30% to about 50% is preferred in the practice of this invention, with a concentration of about 50% providing a superior balance of paint stripping ability and miscibility with carbonate. In this regard, it should be appreciated that a lower hydrogen peroxide concentration of the aqueous solution may require use of cosolvents, surfactants, or the like to provide a miscible final composition.
In one embodiment of this invention, the amount of hydrogen peroxide in the total composition is at least 4 percent by weight. In another embodiment, the amount of hydrogen peroxide in the total composition is at least 10 percent by weight. In another embodiment of this invention, the amount of hydrogen peroxide is at least 15 percent by weight of the total composition or, alternatively, at least 35 percent by weight.
The alkylene carbonate used in the present invention can contain from 2 to 10 carbon atoms. Representative examples of alkylene carbonates that may be employed in the practice of this invention include ethylene carbonate and propylene carbonate. In the practice of this invention, propylene carbonate is preferred.
The dialkyl carbonate used in the present invention may contain from 3 to 25 carbon atoms. The dialkyl carbonate may be of formula Rxe2x80x94CO3xe2x80x94Rxe2x80x2, wherein R and Rxe2x80x2 may be the same or different, and may independently in each occurrence be alkyl of from 1 to about 12 carbon atoms. In one embodiment, the dialkyl carbonate may be dimethyl carbonate, diethyl carbonate, or a mixture thereof.
Concentrated solutions would range from about 8 to about 15 percent peroxide with the balance being water and dialkyl carbonate or dialkyl carbonate and alkylene carbonate.
The compositions of this invention may optionally include an alcohol. Representative examples of such alcohols include methanol, ethanol, propanol, butanol, and benzyl alcohol. In the practice of this invention, benzyl alcohol is preferred. Generally, compositions of this invention contain from 0 to about 90 percent by weight alcohol. For the removal of certain types of coatings, it has been found the efficiency of the carbonate hydrogen deoxidized water solution may be improved by the addition of an alcohol.
The compositions of this invention may include an ether ester. The ether esters that may employed in the practice of this invention may vary widely, and typically contain up to about 20 carbons. The ether groups may be, for example, methyl, propyl or butyl ether groups. Representative non-limiting examples of ether esters that may be employed in the practice of this invention include ethyl-3-ethoxy-propionate, propylene glycol methyl ether acetate, propylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate and dipropylene glycol butyl ether acetate. Ethyl-3-ethoxy-propionate (xe2x80x9cEEPxe2x80x9d) is a representative preferred ether ester which is considered to be safe and of low toxicity. The amount of ether ester used in the practice of this invention may vary widely. Typically the amount is from about 0.1 to about 90 percent by weight of the total composition. In one embodiment, the amount is from about 5 to about 50 percent, preferably from about 5 to about 15 percent.
In certain embodiments of this invention, the compositions contain from about 10 to about 90 percent by weight alkylene carbonate, from about 0.1 to about 20 percent by weight hydrogen peroxide, and from about 0.1 to about 30 percent water. In certain embodiments of this invention containing alcohol, the compositions contain from about 10 to about 90 percent by weight alkylene carbonate, from about 10 to about 90 percent by weight alcohol, from about 0.1 to about 20 percent by weight hydrogen peroxide, and from about 0.1 to about 30 percent water.
In certain embodiments of this invention, the compositions contain from about 10 to about 90 percent by weight dialkyl carbonate, from about 0.1 to about 20 percent by weight hydrogen peroxide, and from about 0.1 to about 30 percent water. In certain embodiments of this invention, the compositions contain from about 10 to about 90 percent by weight dialkyl carbonate, from about 0 to about 90 percent by weight alcohol, from 0 to about 90 percent by weight glycol ether, from 0 to about 90 percent by weight alkylene carbonate, from about 0.1 to about 20 percent by weight hydrogen peroxide, and from about 0.1 to about 30 percent water.
In addition to the components described above, it is contemplated that the compositions of this invention may optionally contain activators such as formic or oxalic acid, thickeners, glycol ethers such as propylene glycol methyl ether (PM), dipropylene glycol methyl ether (DPM), or dipropylene glycol n-butyl ether (DPNB), surfactants, acids or bases, stabilizers, corrosion inhibitors, and other additives commonly used in paint removers.
Non-limiting examples of representative thickeners include cellulose ethers such hydroxypropyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, methyl cellulose, and other alkyl or hydrox alkyl cellulose; silica including colloidal silica; clays such as bentonite and montmorillonite starch; alumina including colloidal alumina; gum arabic; tragacanth; agar, sugar derivatives; high molecular weight polyethylene oxides; guar gum; xanthan gum; polyvinyl pyrrolidone and methyl vinyl ether/maleic anhydride copolymers. It has been found that certain hydroxy alkyl cellulose ethers and certain experimental polymers are particularly effective and resistant to breakdown in the practice of this invention. Such cellulose ethers are available commercially from The Dow Chemical Company under the trade name Methocel(copyright) F4MPRG and Dow""s Experimental Polymer SCS 41067.06. When a thickener is used, the amount of such thickener can vary depending on the desired level of thickening for the given application. In general, the amount of thickener employed is about 1 to about 4 percent by weight.
Non-limiting examples of representative corrosion inhibitors include ethoxylated butynediol, petroleum sulfonates, blends of propargyl alcohol and thiourea. If used, the amount of such corrosion inhibitors is typically up to about 10% by weight of the total composition.
Chelating agents may also be added to the composition of this invention to complex with metal ions which may cause degradation of the peroxide. When used, chelating agents may be used in an amount up to about 10% by weight of the total composition. Representative examples of such chelating agents include, but are not limited to, ethylene diamine tetraacetic acid (EDTA) and its metal salts, diethylene triamine pentaacetic acid, polyphosphates, diketones, hydroxy carboxylic acids and phosphonic acids, and the like.
Non-limiting examples of representative stabilizers for hydrogen peroxide which may be included in the compositions of this invention include C1-4 alkyl anilines, aromatic sulfonic acids, sulfamic acids, sulfones, sulfoxides, sulfolenes, sulfolanes, amino aryl sulfonic acid, benzene disulfonic acid, p-tolyl sulfonic acid, sulfanilic acid, propylene glycol, glycolic acid, glycerine, propionic acid, benzoic acid, cis-4-butenediol, and the like and mixtures thereof The amount of such stabilizers may vary widely when used, and may be used in an amount typically up to about 10% by weight, preferably up to about 1%, of the total composition.
Non-limiting examples of representative surfactants which may optionally be used in the practice of this invention include non-ionic, anionic, cationic aha amphoteric surfactants, such as monocarboxyl cocoimidoazoline, higher alkyl sulfate sodium salts, tridecyloxy poly(alkyleneoxy ethanol), ethoxylated or propoxylated alkyl phenol, alkyl sulfoamides, C10-18 alkaryl sulfonates such as alkylbenzene sulfonates, cocoamphaodipropionate, cetylpalmitic alkanol amides, hydrogenated castor oil, isooctylphenyl polyethoxy ethanol, sorbitan monopalmitate, C8-18 alkyl pyrrolidone, cocoaminoprpionic acid and polyethoxy amino salts thereof When used, the amount of surfactant should be sufficient to render the composition miscible. Typically the amount of surfactant is from about 0.1 to about 10 percent by weight of the total composition.
The compositions of this invention may also optionally contain a wide variety of other organic cosolvents. Likewise, the present invention may be practiced in the absence of one or more of such solvents. Non-limiting examples of representative classes of such other cosolvents include hydrocarbons, glycols, glycol ethers, glycol ether esters, ethers, esters, phenols, glycols, sulfur-based solvents, chlorinated hydrocarbons, aromatic hydrocarbons nitrated hydrocarbons, amides, and ketones. Such cosolvents may be polar or non-polar, may be protic or aprotic, may be cyclic, branched, or straight-chain, and may contain one or more functional groups. Representative examples of common hydrocarbon solvents include hexane, toluene, xylene, and mixtures of aliphatic and aromatic hydrocarbons. Representative examples of common ether solvents include dibutyl ether, ethyl ether, and diphenyl ether. Representative examples of common ester solvents and lactones include material such as butyrolactone, ethyl acetate, butyl acetate, DBE (dibasic ester mixture from DuPont). Representative examples of common phenols include phenol and the Cresols and resorinols. Representative examples of common glycol solvents include ethylene, propylene and butylene glycols as well as methyl propane diol. Representative examples of common sulfur-based solvents include dimethylsulfoxide (DMSO) and sulfolane. Representative examples of common chlorinated hydrocarbon solvents include methylene chloride, methyl chloroform, chlorobenzenes and dichlorobenzenes. Representative examples of common nitrated hydrocarbon solvents include nitroethane and nitropropane. Representative examples of common amide solvents include formamide, dimethyl formamide, acetamide, and dimethylacetamide. Representative examples of common ketone solvents include acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone and methyl isoamylbutone.
It has been found that compositions of this invention that include a DBE are particularly advantageous. These formulations provide an environmentally safe, activated composition. It has been found that compositions containing alkylene carbonate, hydrogen peroxide and DBE exhibit improved paint stripping efficacy relative to benzyl alcohol based strippers. In addition, the alkylene carbonate/hydrogen peroxide/DBE compositions are almost as effective as methylene chloride based paint strippers, but the present compositions are advantageously non-toxic and safer than the methylene chloride based paint strippers.
In general, the DBE used in this invention include aliphatic diesters having a molecular weight of up to about 200. More than one dibasic ester can be used in the present compositions. DBE""s are well known materials and are currently available commercially. In general, the DBE""s used in this invention may be described as being a C1 to C6 dialkyl ester of a C2 to C10 aliphatic di-acid, and particularly a C1 to C4 dialkyl ester of a C2 to C6 aliphatic di-acid. For example, the DBE""s used in the practice of this invention may be derived from various di-acids such as from adipic acid, glutaric acid and succinic acid.
The amount of DBE used in the practice of this invention may vary widely. In general, the amount of DBE may be from about 0.1 percent by weight to about 90 percent by weight, more typically in the range from about 5 to about 50 percent by weight. In one embodiment of this invention, the DBE is present in an amount of about 40 percent by weight of the total composition.
When a given composition containing dialkyl carbonate does not form a miscible composition, a co-solvent may be used to provide a miscible composition. For instance, a glycol ether may be added as a co-solvent in an amount effective to solubilize the components of the mixture. Such glycol ethers may be included for other purposes as well. Such amounts may vary depending on the specific composition of interest, as one of skill in the art may appreciate. The particular type and amount of glycol ether which will afford a miscible composition may be identified by routine experimentation. Typically, the amount of glycol ether employed is less than about 90 percent by weight, and more typically from about 10 percent to about 50 percent. Also, an alcohol or alkylene carbonate maybe beneficially employed as a co-solvent to provide miscible dialkyl carbonate compositions of this invention.
The conditions under which the paint stripping process of this invention may be practiced may vary. Typically, the process will be conducted under ambient atmospheric conditions. Temperatures from 0xc2x0 F. to about 125xc2x0 F., although higher temperatures may be used. The paint remover composition may be applied by any convenient method such as by dipping, spraying, or brushing the composition onto the paint surface. For resistant painted surfaces it may be desirable to apply the composition two or more times to fully separate the paint from the surface. It may be desirable to use a rag, scraper, sand blaster, or the like to fully remove paint chips from the surface after the paint remover composition has been given time to fully act. Alternatively, high pressure water spray may be employed to remove paint chips and residual paint remover composition. It may be appreciated that the time required for the paint remover composition to act will vary due to a variety of factors such as temperature, paint type, and particular paint remover formulation being used. In general, application times are between one minute and one hour, although longer application times may be used.
In the practice of this invention, it is contemplated that a thickener may be admixed into a stripping composition just prior to use. This is particularly desirable if thickeners are employed which are not stable in the hydrogen peroxide compositions for extended periods of time. Admixing may be effected by standard techniques, such as stirring agitation, and rolling. The particular mixing method must be tailored to the specific system being thickened. Likewise, the order or rate of addition of thickener and any other additives or components must be tailored to the specific solvent combination involved.
The following examples are illustrative of this invention and are not intended to be limit the scope of the invention or claims hereto. Unless otherwise denoted all percentages are by weight. In the tables, xe2x80x9cN/Axe2x80x9d denotes xe2x80x9cnot available.xe2x80x9d